全文获取类型
收费全文 | 993篇 |
免费 | 106篇 |
出版年
2017年 | 10篇 |
2015年 | 25篇 |
2014年 | 19篇 |
2013年 | 27篇 |
2012年 | 42篇 |
2011年 | 29篇 |
2010年 | 19篇 |
2009年 | 26篇 |
2008年 | 22篇 |
2007年 | 30篇 |
2006年 | 23篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 24篇 |
2002年 | 30篇 |
2001年 | 40篇 |
2000年 | 41篇 |
1999年 | 24篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 15篇 |
1993年 | 13篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 27篇 |
1989年 | 20篇 |
1988年 | 21篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1981年 | 25篇 |
1980年 | 31篇 |
1979年 | 15篇 |
1978年 | 41篇 |
1977年 | 23篇 |
1976年 | 29篇 |
1975年 | 25篇 |
1974年 | 28篇 |
1973年 | 20篇 |
1972年 | 9篇 |
1971年 | 8篇 |
1970年 | 7篇 |
1969年 | 10篇 |
1968年 | 13篇 |
1967年 | 7篇 |
1966年 | 7篇 |
排序方式: 共有1099条查询结果,搜索用时 359 毫秒
61.
Anake Kijjoa Astréa M. Giesbrecht Otto R. Gottlieb Hugo E. Gottlieb 《Phytochemistry》1981,20(6):1385-1388
The trunk woods of two Amazonian Myristicaceae, Virola minutiflora and V. elongata, contain respectively 1-(2-hydroxy-4-methoxyphenyl)-3-(3,4-m 相似文献
62.
Marden A. De Alvarenga J. Jerônimo Da Silva Hugo E. Gottlieb Otto R. Gottlieb 《Phytochemistry》1981,20(5):1159-1161
The structure of micrandrol-C from Micrandropsis scleroxylon (Euphorbiaceae) is revised to 2,6-dihydroxy-7-methyl-1-methylthiophenanthrene. This and other micrandrols are probably diterpenes in view of their co-occurrence with micrandrol-D, the hemiketal of 1,2,3,4,9,10-hexahydro-6-hydroxy-4a-hydroxymethyl-1,1,7-trimethy-2-oxophenanthrene. 相似文献
63.
64.
65.
The genomic and antigenomic RNAs of hepatitis delta virus are capable of self-cleavage and show no significant sequence similarities to other known self-cleaving RNAs. We have derived an antigenomic delta RNA which cleaves to completion in 15 s in 9 mM magnesium at 37 degrees C and is capable of efficient self-cleavage in concentrations of formamide as high as 20 M. Cleavage in high concentrations of denaturant is dependent upon the presence of a polypurine sequence element, GGAGA, located between 81 and 85 nucleotides downstream of the cleavage site. Mutation of the initial G81G82 to C81C82, or removal of the sequence element, results in a loss of the ability to cleave in high formamide concentrations. Changing the final U-2C-1 of a pyrimidine-rich region, UCUUC, just upstream of the cleavage site, to G-2G-1 severely affects the self-cleavage, but introducing the two mutations, GG to CC and UC to GG, into the same molecule, restoring potential base pairing, partially restores the formamide stability. Relocating the GGAGA sequence upstream of the cleavage site also results in partial restoration of the formamide cleavage. Although the GGAGA sequence is important for self-cleavage under denaturing conditions, it does not appear to be necessary for HDV RNA cleavage in normal buffer conditions. 相似文献
66.
67.
JoÃo B. Fernandes Otto R. Gottlieb Lucia M. Xavier 《Biochemical Systematics and Ecology》1978,6(1):55-58
The trunk wood of Aniba riparia (Nees) Mez (Lauraceae) contains flavokawin-B, (2S)-pinostrombin, (2S)-5, 7-di-O-methylpinocembrin, (2R, 3R)-5, 7-di-O-methylpinobanksin, izalpinin and 3,5, 7-tri-O-methylgalangin. Structural comparison of these flavonoids with the pyrones and neolignans, which characterized all previously examined Aniba spp., leads to a chemical classification of the genus. 相似文献
68.
Genetic Control of Pattern Determination in Drosophila. the Action of Hairy-Wing 总被引:3,自引:2,他引:1 下载免费PDF全文
Frederick Jay Gottlieb 《Genetics》1964,49(5):739-760
69.
70.